The best way to let Galaxy manage dependencies from dev and admins perspective is to use Conda package manager, see planemo docs for tool developer details regarding that matter.

To have Galaxy actually install the dependencies with the tool the tool itself needs to be in the Tool Shed and installed into Galaxy via the Admin interface by an administrator. The software dependency also has to be available in one of the default conda channels. Check the bioconda to see whether your dependencies are packed there.

That said if you pip install the dependencies on your machine instead and the system user that runs Galaxy has them on the $PATH Galaxy will find and run it when the tool needs it. However you are losing a lot of reproducibility and convenience for the user/admin.